Don't hide nullability problems behind a cast

[BraisGabin]

Expected Behavior of the rule

Noncompliant:

fun foo(bar: Any?) {
  val x = bar as String
}

Compliant:

fun foo(bar: Any?) {
  val x = bar!! as String
}

Context

The cast operator can hide null problems in your code. I propose a rule that forbid any cast from a nullable type to a non-null type. If you want to do that you first should cast from nullable to non-null and then do the cast as shown in the example.

The idea is to write code that show that it could fails for two things (nullability and type) and not just one (cast).

I had this idea reading #3479 so they are related but they are not the same.

[github-actions]

This issue is stale because it has been open 90 days with no activity. Please comment or this will be closed in 7 days.

[atulgpt]

Hi @BraisGabin I am willing to implement this issue, should I proceed and will your review the PR?

[BraisGabin]

Please, go ahead! I'll review it.

[atulgpt]

Hi @BraisGabin added my fix at #5653. This PR might contain some issues as this is my first time working with Kotlin PSI and detekt. Thanks for reviewing this PR